Etching is widely known and used in metal and alloy processing and, in particular, electronics manufacturing. For instance, etching is commonly used in fabrication of magnetic recording heads. The etching may be accomplished by a number of methodologies, including chemical (wet) etching, electrochemical (wet) etching and (dry) ion milling.
During chemical (wet) etching, a substrate is submerged in a strong acid or alkaline solution and the surfaces of the substrate exposed to the solution are etched away. During electrochemical (wet) etching, a substrate is also submerged in a strong acid or alkaline solution and the surfaces of the substrate exposed to the solution are etched away. However, unlike chemical (wet) etching, once the substrate is submerged in the solution, a net anodic current is applied to the substrate to facilitate the etching process, where the net anodic current comprises a large partial anodic current component and a smaller partial cathodic current component.
During (dry) ion milling, the etching is facilitated by bombarding the surface of the substrate with submicron ion particular (e.g., Argon ions). Typically, as the ions bombard the substrate surface, the material disposed on the surface is etched away. The ion milling is usually performed while the substrate is in a vacuum chamber, and the substrate is placed on a rotating platform to ensure uniform etching of the substrate.
Depending on the substrate and the material on the substrate being etched, either of these etching methods may use protective layers (e.g., photoresist layers or hardmask layers) to protect underlying layers of the substrate from the etch process.